I have an old jumpbox, maybe 6-7 years old. Used very few times. It is not a lithium but rather an AGM battery. I seems like it has just died and rechrging isn’t doing anything. The battery itself goes into maintenance mode after charging.
What is the best way to test it? Run a load off of it? Turn it on and use a voltmeter?
Will an AGM jumpstarter/battery just die of old age even with very few cycles on it?
Did I kill it by going months without recharging it?
Discharging an AGM battery to zero will kill it.
You might be able to get some life out of it by charging and discharging it a few times, but it’s probably toast.
And a lead acid battery (AGM included) will self discharge over time. So yes it’s likely dead
Even a more modern Li-ion will need a periodic recharge. They are not “Buy once, throw in trunk, use whenever forever” products. They are “Buy the first time, recharge quarterly-ish, use whenever for a few years, buy again” products.
Yes, I have an old jump box and the battery eventually stopped taking a charge. A bit of research showed it was using a golf cart battery, and I could get a replacement much cheaper than buying a new jump box.
Good point. Any of the sealed lead acids should be replaceable if you’re OK with a screwdriver.
OTOH …
I have an Amazon-branded ~400W UPS I bought about 4 years ago. Whose battery had died, no longer holding a charge. Damn. OK, open 'er up to see what size I need. Has a nice legible model number, isn’t hot-glued into place and the connectors are simple pull-offs. Yaay, this oughta be easy. Nope. It’s a discontinued form factor. Neither Amazon nor Batteries Plus nor the internet at large can sell me another one.
So I bought the next smaller size that will fit the space physically in all 3 dimensions. Which has about 1/2 the Wh capacity. Oh well; it’s really just a glorified surge protector for my internet hookup and desktop docking station and monitor. If it lasts long enough to prevent router/modem reboots during a power flicker that’s my 98% use case.
So anyone looking to replace the battery in a dead jumpbox may be dissappointed. But it’s sure easy enough to try.
Looks like I need a new one then.
A new battery for sure. A new box, maybe not.
Rather: use the one your neighbor bought.
If you are going to spend money to have a more reliable battery system, spend it on replacing your main car battery in time.
The one my neighbor bought will not be in my car when it won’t start at the airport after a trip. Jumpboxes, like a spare tire, are in fact a valuable accessory to carry in one’s car. And, like spare tires, they need to be properly charged / inflated to be of any use. And they only stay that way if you pay attention to maintaining them that way at a reasonable interval.
Agree that a LOT of jumps are caused by main batteries being used until failure, rather than being proactively replaced early when they’re getting elderly but not yet decrepit. Imagine continuing to drive on tires until each in turn has a blowout after all the tread has been worn off. Pretty wacky idea, but you’re right that’s how many people treat their main battery.
OTOH, there are lots of ways for a modern car to drain an otherwise youthful healthy battery.
There’s a fundamental principle here.
No matter what type, batteries are consumables and expendables. If you have a rechargeable battery device long enough, the answer to “does it die over time” is inevitably “yes”.
i’m just balking at the idea that someone with a dead battey would have a charged jumpbox in the trunk.
In my world it is something you borrow from a neighbor to help a buddy at the airport or borrow from a buddy to help your neighbor at the airport.
Some folks are good at being prepared. Some are not. You’re sure right about that.
For my part I find the idea of me calling a friend from the airport asking for help to be well beyond unthinkable. The hassle I’d be imposing on them would waste most of a day for both of us. And there’s about a 80% chance it’s either stupid-early in the morning or stupid-late at night as I’m having this problem.
Vive le difference!
Yeah, if you’re not responsible enough to keep your car battery maintained and charged, your jumpbox is probably in no better shape.
I bought a jumpbox cheap at a garage sale years ago, because at the time I had a motorboat I used for fishing. Even though I routinely trickle-charged the boat battery, I was always nervous I’d run the trolling motor too much and drain the boat battery down to the point it wouldn’t start up the main motor when I was at the opposite side of the lake from the launch. So I figured the jumpbox would be a good backup.
Unfortunately, as I should have suspected, the previous owner clearly hadn’t taken proper care of the jumpbox, because it wouldn’t hold a charge.
The thing is, most such UPS units are for 2 purposes - if there’s that momentary power drop during a storm where the lights all blink - it will keep the computer from resetting. If the power is out for a while, it will give you time to save and shut down cleanly. (Some have the utility to run in the background to monitor the UPS status, and if the power has been out for X minutes, time for an orderly shut down. Typically this was for servers. )
It’s depending on location and power company, but where I am I haven’t seen a lot of those really long power outages, probably less than one a year. We have almost none of those lesserinterruptions 1 or 2 minutes - it’s eaither a blink or it’s out for half an hour or more.
I suppose it’s a good idea once in a while to test the UPS to see how long it really lasts, and give it an opportunity to drain and recharge.
That’s certainly been my experience. Which is why even the much less capable bastardized UPS I now have meets my 98% use case.
It is. I had not tested mine in a couple years. And then I unplugged the power cord to add an extension cord ahead of it and the UPS went “beep, bloo-oorp” then everything connected to it went dark. Oops.
I have one of those things. Came with the car. Buried under a panel in the back.
Don’t think I’ve ever looked at it.
I suspect it’s never been charged.
I guess I better check that.
But, I have this much easier tool. A cel phone.
If I couldn’t get a family or friend, I’d call my roadside assistance. Since I pay for it.
Ultimately it depends on battery chemistry and quality. I have one of the early iPods (White box, 80GB hard disk) and about 20 years later it still runs off the internal battery. A lot of older stuff the rechargeable battery has rung down the curtain and joined the choir invisible.
One word of caution. Many booster packs have a safety feature where they won’t power on unless the jumper cables detect some nominal voltage. This is to prevent live booster cables from accidentally shorting out or shocking you. If the battery is close to 100% flat they won’t work. Fortunately this is rare but it can happen. Ask me how I know! 
If you’re in a long term parking lot and need a charge, the attendant may be able to do it. They often have a jump box. They may also be able to do tire inflation.
The lithium jump boxes may be more convenient. They’re smaller and easier to charge. They can also be used as a portable charger for your phone and tablet. It seems to me like they hold a charge longer than my lead acid jump box. But a downside is that they may not be able to provide as many jumps.